A SIM lock, simlock, network lock, carrier lock or (master) subsidy lock is a technical restriction built into GSM and CDMA mobile phones by mobile phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networks. This is in contrast to a phone (retrospectively called SIM-free or unlocked) that does not impose any SIM restrictions.
Generally phones can be locked to accept only SIM cards with certain International Mobile Subscriber Identities (IMSIs); IMSIs may be restricted by:

Mobile country code (MCC; e.g., will only work with SIM issued in one country)
Mobile network code (MNC; e.g., AT&T Mobility, T-Mobile, Vodafone, Bell Mobility etc.)
Mobile subscriber identification number (MSIN; i.e., only one SIM can be used with the phone)Additionally, some phones, especially Nokia phones, are locked by group IDs (GIDs), restricting them to a single Mobile virtual network operator (MVNO) of a certain operator.
Most mobile phones can be unlocked to work with any GSM network provider, but the phone may still display the original branding and may not support features of the new carrier. Besides the locking, phones may also have firmware installed on them which is specific to the network provider. For example, a Vodafone or Telstra branded phone in Australia will display the relevant logo and may only support features provided by that network (e.g. Vodafone Live!). This firmware is installed by the service provider and is separate from the locking mechanism. Most phones can be unbranded by reflashing a different firmware version, a procedure recommended for advanced users only. The reason many network providers SIM lock their phones is that they offer phones at a discount to customers in exchange for a contract to pay for the use of the network for a specified time period, usually between one and three years. This business model allows the company to recoup the cost of the phone over the life of the contract. Such discounts are worth up to several hundred US dollars. If the phones were not locked, users might sign a contract with one company, get the discounted phone, then stop paying the monthly bill (thus breaking the contract) and start using the phone on another network or even sell the phone for a profit. SIM locking curbs this by prohibiting change of network (using a new SIM).
In some countries, SIM locking is very common if subsidized phones are sold with prepaid contracts. It is important to note, however, that the technology associated with the phone must be compatible with the technology being used by the network carrier. A GSM cell phone will only work with a GSM carrier and will not work on a CDMA network provider. Likewise, a CDMA cell phone will only work with a CDMA carrier and will not work on a GSM network provider. Note that newer (2013+) high end mobile phones are capable of supporting both CDMA and GSM technologies, allowing customers to use their mobile devices on any network. Examples of these mobile devices are the Apple iPhone 5c, 6 and newer, Motorola's G4, G5, X Pure, Samsung's Galaxy S6, S7, S8 smart phones, mostly phones based on a Qualcomm Snapdragon chipset or radio.
In some jurisdictions, such as Canada, Chile, China, Israel, and Singapore, it is îllégâl for providers to sell SIM locked devices. In other countries, carriers may not be required to unlock devices or may require the consumer to pay a fee for unlocking.
Unlocking the phone, however, is almost universally legal. Additionally, it is often legal for carriers to force SIM locks for certain amounts of time, varying by region.

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  1. A

    Closed Simlock

    help po pano maayos eto simlock yan po.nakalagay pag insert ko ang sim na TM
  2. D

    Closed Patulong po maopen line ng pocket wifi - huawei viva 4g lte

    Good day po, Patulong din po please, inuunlock ko po yung sim kaso hinihingan ako ng code. HUAWEI VIVA 4g LTE din po. Ito po yung IMEI at model sa baba IMEI: 864695030712741 Model: E5577Cs-321 Malaking tulong po ito samin, salamat po !
  3. C

    Closed Simlock to unlock

    Ano po code ng sim na na lock. Kailangn po kasi .masyado rply asap IMEI: 867262023262718 Model: E5577Cs -321
  4. K

    Closed Sim lock

    meron akong iphone 5s at naka lock sa sprint usa may pag asa pabang ma factory unlock to ? help naman po
  5. E

    Closed Docomo dtab d-01g sim unlock

    Guys patulong naman aq sa Docomo dtab d-01G, hindi gumagana ung sim card ... pano q po ito magagamit at malalagyan ng sim card: imei: 866118022921988
  6. S

    Closed [help] pano po maiwasan ang simlock?

    Aiming to be an established member. Ang tanong ko po ay paano ba maiiwasan ang simlock (smart)? (Currently registered to play100 & aoc20)
  7. H

    Closed Simlock(smart) phone

    Magandang gabi mga paps! Alam nyo po ba pano mag unlock na simlock(smart) na phone (O+)? Pa tut naman. Thanks ☺
  8. E

    Closed Simlock code!

    Sana mga master mabigyan nyo ako ng working code... Zain Middle East Telecom Huawei E5577s-321 IMEI: 867262021149644 Salamat po.
  9. S

    Closed Sino may alam paano mag unlock ng simlock sa phone?

    Phone ko ay O+ Crunch, ang sim 1 smartlocked pero ang sim 2 openline matanong ko lang paano po tinatanggal ang simlock? ang mga technician sa palengke kaya nila so kaya rin ba natin? paano nila ginagawa?
  10. N

    Closed Unlock mobile mifi/wifi (huawei)

    Hi pips! May naunang post na po about sa unlocking of mobile mifi/wifi, eto po Dagdag ko lang po sa tutorial, para sa following models: Huawei E3272 Huawei E3531 Huawei E5372 Huawei 823F МТС 824FT МТС 423S Megafon...
  11. Y

    Closed Alcatel one touch pixi 7 - t-mobile sim unlock

    (Ayan di na capital) Ask ko lang po if pupwede ba na palitan ng firmware yung one touch pixi 7 pra ma open line? naka sim lock siya sa Tmobile
  12. N

    Closed Unlock simlock

    Device name : E5330Bs-2 IMEI : 868988029627913 IMSI : 515032421919728 pa unlock po.
  13. M

    Closed Smartbro pocket wifi

    Mga bro sis paano po ma openline ang pocket WiFi kopo smartlock
  14. N

    Closed Nokia lumia 52 openline

    Pa Help po Sinong marunong kung pano e open line ang nokia 521 o link man lang sa mga code salamat ng marami sa papansin at totulong ..
  15. D

    Closed Change os? sim unlocked?

    May tanong lang po ako, Ang cp ko po ngayon ay Samsung SM-J120H, naka simlock po sya sa sun cellular, version po ng android ko po ay 5.1.1 . Ngayon po, pag pinapalitan ko po ng OS yung android ko, mawawala po ba yung simlock nya or magstay pa din sya dun sa cp ko?? Thanks po sa sasagot
  16. D

    Closed Sim locked phone. sun cellular

    Mga bossing, may app po ba or trick para mabasa nung cellphone ko yung globe kong sim card?? Naka sim lock kasi sya sa sun cellular... Pa help naman po. May ibibigay po ako sa kung sino tutulong sa kin. TnT user dapat.. kung alam nyo na to kung ano sinasabi ko, edi okay. :) :) :) Gamit kong...
  17. F

    Closed iCloud issue at galing ibang bansa

    Pahelp naman mga ka phcorner kung anong dapat kong gawin sa iPhone 5s ko. Newbie lang po ako sa iPhone eh, binigay lang po ng pinsan ko. May icloud issue din po sya at galing ibang bansa kaya daw di po bumabasa ng sim dito. Need help asap :'( Thank you po.
  18. V

    Help Samsung sgh - f266

    mga kaPH help naman po. meron po kasi ako samsung sgh F266 from FIDO, naka SIMLOCK po sya, hindi ko magamit any sim na isalpak. may alam po ba kayong paraan para maunlock ito. bibigyan ko po ng load ang makakatunlong sakin. salamat po.